The keel is the back bone of any water craft and lies fore and aft along the center line of the bottom. In sailing craft as opposed to power boats, keels are designed to increase lateral resistance. This is the hulls ability to resist being driven sideways by the wind. The resistance increases by designing keels short and deep (i.e. high- aspect- ratio) rather than long and shallow. The centerboard is a form of drop keel that pivots into the water from a well situated over the keel. When the board operates in a similar style to a knife in a sheath it is called a daggerboard. Each system has advantages and disadvantages. Specifically, centerboards pivot and will kick-up when the board strikes an object. This feature is very convenient and has saved many centerboard craft from annoying and sometimes serious damage. Ideally, the centerboard can be pivoted up and out of the way within the hull allowing for beaching and transporting without removal. A disadvantage of centerboards is the turbulence caused by a large open well slot in the hull bottom which is needed to accommodate the pivoting centerboard. Some centerboards are designed to completely fill the well slot at all angles of pivot which eliminates the need for gaskets. The pivoting gasketless design is very convenient and trouble free, however the resulting board shape is less efficient. Conversely, some centerboard designs have an efficient board shape but the remaining open well slot must be sealed to reduce turbulence. Many high-performance centerboard craft go to great lengths to seal open well slots in order to reduce turbulence. Gaskets are often used to seal well slots but are a continual maintenance problem and usually prohibit be, aching. Modem hydrodynamic theory says that a high-aspect-ratio, (i.e. large depth to width ratio) board is more efficient for windward points of sail. Daggerboards, which move up and down vertically, can be very efficient because they can have a high-aspect ratio board without a large well slot and no gaskets. The daggerboard can also be used in a wide range of positions from fully down to nothing showing below the hull. This makes for a very efficient gasketless system. The main disadvantage of a daggerboard is its inability to automatically kick up if struck by an object. The potential for serious damage is always present. Another very annoying inconvenience is the protruding daggerboard above deck in all but the full down position. Also, while transporting, the daggerboard must be removed from the hull resulting in handling and storage problems.
The present invention combines all the advantages of both systems, resulting in the ease, safety and convenience of the centerboard and the performance of the high-aspect-ratio, gasketless daggerboard which incorporates the following objects and advantages:
(a) to provide a high-performance centerboard system which combines the performance potential of a traditional daggerboard system and the convenience and safety of a traditional centerboard system; PA1 (b) to provide a high performance centerboard system with a minimum of moving parts; PA1 (c) to provide a centerboard system that is easy to use in a wide range of sailing conditions; PA1 (d) to provide a centerboard system that is capable of being used on high performance as well as pleasure craft; PA1 (e) to provide a centerboard system that is capable of being made using light weight and high-strength materials; PA1 (f) to provide a centerboard system that minimizes the well-slot size; PA1 (g) to provide a centerboard system that requires no gaskets; PA1 (h) to provide a centerboard system capable of being used on all sizes of craft; PA1 (i) to provide a centerboard system which can be easily operated by hand, however, if size requires, be operable with some mechanical advantage device. PA1 (j) to provide a centerboard system that is easy to manufacture;
Further objects and advantages are to provide a high performance centerboard system which can eliminate or reduce the disadvantages of traditional daggerboard/centerboard systems as well as those reviewed as prior art. One of the aims of this invention is to reduce disadvantages such as protruding boards into inconvenient places, excessive weight, large well slot sizes, gaskets, too many parts, impractical for high performance water craft, not user-friendly, not beachable, not easily removable and more. Still further objects and advantages of my invention will become apparent from a consideration of the drawings and ensuing description.